Following a near-miss incident during plant sanitisation activities, a specialist sanitisation contractor engaged E.S.M. to undertake a comprehensive engineering study into the electrical safety risks associated with high-pressure jet washing of electrical equipment.

Jet washing is an essential component of sanitisation processes across multiple industries, including food processing, dairy and livestock operations. As a service provider, the client operates within facilities owned and maintained by others, relying on plant operators to ensure electrical installations are compliant and appropriately de-energised prior to washing. The incident highlighted the need for a structured and defensible assessment of electrical risk within this shared-responsibility environment.

Regulatory and Technical Framework

The study commenced by establishing the legislative and technical context governing electrical hazards associated with jet washing. E.S.M. advised the client on applicable duties under Work Health and Safety and Electricity legislation, clarifying the respective responsibilities of the sanitisation contractor and plant owner/operator.

A detailed review of relevant Australian Standards and industry guidance was undertaken, including:

  • AS/NZS 3000 – Electrical Installations (Wiring Rules)
  • AS 4233.1 – High Pressure Water Jetting Systems
  • AS/NZS 4836 – Safe Working on or Near Low Voltage and Extra Low Voltage Electrical Installations and Equipment
  • AS/NZS 3017 – Electrical Installations – Verification by Inspection and Testing
  • AS 60529 – Degrees of Protection Provided by Enclosures (IP Code)

This review identified the typical electrical safety control measures required in industrial environments. E.S.M. then interpreted these requirements specifically in the context of high-pressure jet washing operations, identifying where additional clarification or engineering assessment was required.

Site Investigation and Operational Review

E.S.M. conducted site visits to observe live jet washing operations and inspect representative electrical installations. This practical engagement, combined with a review of the client’s existing risk assessments, safe work procedures and training materials, enabled a clear understanding of:

  • The operational workflow
  • The nature of electrical hazards present
  • Existing control measures and their limitations

This ensured the study was grounded in real-world operating conditions rather than theoretical assumptions.

Bow Tie Analysis

Using the information gathered, E.S.M. developed a formal Bow Tie risk model to map the credible pathways by which jet washing water could contact energised electrical equipment and result in harm.

The analysis identified:

  • Threats leading to water contacting live conductors
  • The top event (loss of electrical isolation or ingress into live equipment)
  • The potential consequences, including electric shock or electrocution
  • Preventative and mitigative control measures

The study clearly distinguished between barriers and safeguards. A control measure was only classified as a barrier if it was:

  • Effective – capable, on its own, of preventing or mitigating the hazardous event
  • Independent – not reliant on the performance of other barriers
  • Auditable – subject to verification and supported by defined performance standards

Measures that supported the ongoing effectiveness of barriers, but did not independently prevent or mitigate harm, were classified as safeguards.

Each barrier was assessed for robustness and reliability, and associated safeguards were mapped to defined responsibilities, procedures and training requirements. The result was a structured and defensible framework demonstrating that all credible pathways to harm were addressed through effective and auditable controls.

Engineering Assessment – Fluid Mechanics and Electrical Breakdown

Several identified controls required deeper engineering evaluation. In particular:

  • The ability of high-pressure water jets to penetrate IP-rated enclosures
  • The potential for a water jet stream to form a conductive path between an energised source and the operator

These issues extend beyond typical qualitative risk assessment and required detailed technical analysis.

E.S.M. undertook fluid mechanics modelling and calculations to compare:

  • Jet washer output pressures and velocities
  • Water jet coherence and break-up regimes
  • Test conditions used in IP rating verification
  • Dielectric breakdown characteristics of water in various flow states

This analysis provided an objective, engineering-based foundation for determining when jet washing practices could be considered acceptably safe, and under what operational constraints.

Outcome

The study delivered:

  • Clear engineering-based recommendations for safe jet-washing practices
  • Defined procedural, verification and training requirements
  • Clarified responsibilities between contractor and plant operator
  • A documented and defensible safety case supporting the continued use of jet washing in plant sanitisation

By combining regulatory analysis, structured risk modelling and detailed engineering calculations, E.S.M. provided the client with confidence that its operations could be conducted safely, consistently and in compliance with applicable standards.